See, I KNEW fluorite was the ultimate astronomical element!

[LewisM]

http://www.skyatnightmagazine.com/news/fluorines-amazing-origins-revealed

:)

Ah fluorine... mix it with Calcium, and you have sweet, SWEET optics, and minty fresh breath.

[AstralTraveller]

Combine it with hydrogen and you have the strongest acid known. It is perhaps the only thing I am aware of that will dissolve silicates (possibly boiling anhydrous NaOH also works). For this reason it is used in geochemical research. It is also incredibly toxic and will kill you as soon as look at you. It is absorbed through the skin and causes organ failure. Direct contact with even a few mL is generally fatal. [Terry in the OSL lab etches mineral grains with HF in near darkness, the red light is so faint even an experienced astronomer would find it daunting. He can keep it.]

The discovery of fluorine is an interesting and tragic tale. Researchers often accidentally actually made HF and then unwittingly exposed themselves to it. There were several deaths. Also the HF attacks glass apparatus and so it wasn't until someone built a set of pure Pt apparatus that it was isolated.

[RB]

So don't lick your refractors Lewis.

:P

[PlanetMan]

I probably misread the article but it doesn't actually discuss fluorite in refractor optics - I thought the whole idea of fluorite particle lens (ie FPL 51 53) was to get the good benefits of fluorite crystal without the hiccups (fragile, brittle, expensive, toxic etc)

[Satchmo]

Yep , Flourite is not ideal - brittle and open to moisture attack . I broke the flourite element in my Celestron /Vixen refractor when giving the dew hood a bit of tap when I cross threaded it .

[PeterEde]

Hydrofluric acid dissolves bone from within according to a lab tech friend and the only way to stop it is amputation?

[LewisM]

No, it wasn't specifically mentioned - just about the discovery of fluorine origins... which I branched off on. ANYWAY...

FPL53 only has roughly 20% (MAXIMUM) or fluorite in it, so it only proffers SOME of the good Fl characteristics. FPL53 still shows significantly more light scatter than a CaF2 element does. I haven't looked at O'Hara's site for a while, but I think FPL51 - the most common glass in Chinese refractors - only contains roughly 4 to 8% fluorite.

I found this iStar forum thread of interest: http://istarscopeclub.proboards.com/thread/247/twisting-facts-caf2-fluorite-apos

Well worth the read if you are interested in the differences between CaF2, FPL51 and FPL53 glasses.

Andrew - I make all my vodka shot glasses out of CaF2 - slamming them on the table or setting Ouzo alight is guaranteed to shatter them into non-reusable status ;)

[RickS]

Must be magical stuff indeed! Apparently, it's not constrained by the laws of Physics ;)

[multiweb]

Nothing beats a good vodka spaced triplet.

[RickS]

Now you're talking, Marc, although I find that a 20 year old single malt offers better colour correction :thumbsup:

[LewisM]

Uh ah - colour DISTORTION :)

[cometcatcher]

You're all spoiled nowdays. In the good old days of the wild west and pirates, we used F 100 to correct for stuff. Sometimes there was minor droop. :P

[RB]

Hence my preference for Ouzo Doublets.

:P

[LewisM]

You see double after an Ouzo doublet. 2 pot screamer...:drink: